There are two types of AC induction motors commonly used in industry: single-phase motors and polyphase motors. Among the polyphase groups, three-phase induction motors are the most commonly used. In a single-phase motor set, five different sub-groups are usually used, which are split-phase, capacitor-start (CS is a variant of split-phase motor), shaded pole (shaded pole) ), permanent split capacitor (PSC, permanent split capacitor) and capacitor start-capacitor run (capacitor start-capacitor run, CSCR is a variant of PSC motor).
Typically, split-phase, capacitor-start, and capacitor-start capacitor-run motors are excluded in variable speed control situations because they all have a start winding or a contact that needs to reach 75% of the motor’s full load speed before the start winding is disconnected, at When controlling the speed, it is usually less than 75%. If the starter switch does not open, the contacts or starter winding will burn out quickly and the motor will overheat and stop.
When deciding which induction motors to use, there are mechanical methods that allow these motors to reach their maximum speed, which theoretically could be used if they were never slow enough to re-engage the starter contacts during normal operation. The rest of the motor, shaded pole, permanent split capacitors and polyphase, is the best choice for choosing a motor that will be speed controlled. The shaded pole motor is the most economical of the three to use due to its inherent design, but it is only available under 1/4 horsepower. It also has a low starting and running torque and is inefficient due to limitations. Therefore, for single-phase operation with more than 1/4 power and/or high operating torque, permanent split-phase capacitor motors are often used. This type of motor is one of the more expensive single-phase motors, but it is very reliable, has good running and starting capabilities, and allows speed to be controlled electronically. Permanently split capacitor motors function closest to three-phase motors. way of working.
Three-phase motors are available in both partial and full horsepower, but generally, the power savings won’t exceed their cost until they get into the overall horsepower range. It works basically the same way as a single-phase motor, not one hot wire, but three, the control speed needs to be different from a single-phase controller, and the functions of single-phase and three-phase are slightly different.
There are generally four ways to control the speed of a motor. The simplest is a variable speed motor. The remaining three groups are passive device speed control, solid state controls and mechanical devices. Each method is unique and is found throughout the industry. use. Regardless of the application, generally check with the motor manufacturer what the speed control standard is, as some motors are not equipped for speed control. Also, be aware of all safety concerns such as thermal overload protection as part of the speed control system. There is often a lot of heat generated by the motor, when using the speed controller, to prevent accidents or damage, it is recommended that the overload protector can be part of the motor or the controller itself.
in conclusion
As the use of industrial motors has evolved over the years, so have the ways to control speed, to get the right choice of speed control, what type of motor it can accommodate, and the expense/efficiency constraints involved, some controllers may be less expensive, Not as user friendly as other controllers, but still gets the job done.
Post time: May-07-2022